My new PSA upper is still TIGHT on the rear pin on my DPMS 'factory' lower.. I use an allen-key to align (from opposing side) and tap lightly in with a jeweler weight hammer to get it in..
Of course I think its slowly working IN.. I've only cleaned it like 6 times in 1000 rounds.. (or 4 range trips)
I like the tight fit.. which I hear is better.. but if you got to BEAT them in all the time.. thats an issue.. a dowel with 220 grit may be your best friend.. IMHO..
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US Navy Vet. 1988-1992
PSA/BCM 5.56 [Shelly],
Marlin P70 Papoose, Sig 2022
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